Method for testing multicore cable, method for manufacturing multicore cable assembly, and multicore cable test device

ABSTRACT

A method for testing a multicore cable including a single common shield covering plural insulated wires to identify a correspondence relation between one end portion and the other end portion of the insulated wires exposed from both ends of the multicore cable. The testing method includes allowing the common shield to have a same potential as a measurement system ground, inputting a test signal, by capacitive coupling, to an end portion of the insulated wire under test among end portions of the insulated wires exposed at one end of the multicore cable, and measuring voltages of output signals output by capacitive coupling respectively from end portions of the insulated wires exposed at the other end of the multicore cable, and identifying the other end portion of the insulated wire under test based on the measured voltages.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on Japanese patent application No.2018-001334 filed on Jan. 9, 2018, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a method for testing a multicore cable, amethod for manufacturing a multicore cable assembly, and a multicorecable test device.

2. Description of the Related Art

A multicore cable is known in which numerous multiple insulated wireseach having an insulation around a conductor are covered with a singlejacket. Also, a multicore cable used for, e.g., medical probe cables isknown which has several tens to several hundreds of insulated wires(coaxial wires etc.).

For the multicore cable having the numerous insulated wires, it isdifficult to use a color code so that every insulated wire has adifferent color insulation. In addition, in case that the insulatedwires are twisted together inside the multicore cable, each insulatedwire is not located at the same position. Therefore, when connecting amulticore cable having numerous insulated wires to connectors or circuitboards, a test method is required to somehow identify a correspondencerelation between one end portion and the other end portion of each ofthe insulated wires exposed from both ends of the multicore cable.

As a test method to identify the correspondence relation between one endportion and the other end portion of insulated wires contained in themulticore cable, for example, there is a method in which a test signalis input to one end portion of a given insulated wire and voltage outputfrom the other end portion is measured.

To test the multicore cable having numerous insulated wires, when aconductor of each insulated wire is exposed at an end portion and anelectrode for supplying a test signal is directly brought into contactwith the conductor, it is necessary to bring the electrode into contactwith the conductor of every insulated wire to identify thecorrespondence relation and it thus takes very long time for the test.Thus, the test to identify the correspondence relation between one endportion and the other end portion of insulated wires contained in amulticore cable having numerous insulated wires is desired to beconducted by a method in which an electrode is placed on an insulationand an AC test signal is input to a conductor by capacitive couplingwithout contact (see, e.g., JP 2004/251771 A).

SUMMARY OF THE INVENTION

In the method where the AC test signal is input to the conductor withoutcontact, if numerous insulated wires are highly densely arranged in themulticore cable and if input of an AC test signal and output of an ACoutput signal are performed without contact, crosstalk between theinsulated wires increases. As a result, the correspondence relationbetween one end portion and the other end portion of the insulated wiressometimes cannot be accurately identified due to the crosstalk.

It is an object of the invention to provide a method for testing amulticore cable that can reduce the effect of crosstalk when performinginput of an AC test signal and output of an AC output signal withoutcontact so as to accurately identify a correspondence relation betweenone end portion and the other end portion of insulated wires, as well asa method for manufacturing a multicore cable assembly and a multicorecable test device.

According to an embodiment of the invention, a method for testing amulticore cable comprising a single common shield covering a pluralityof insulated wires to identify a correspondence relation between one endportion and the other end portion of the insulated wires exposed fromboth ends of the multicore cable comprises:

allowing the common shield to have a same potential as a measurementsystem ground;

inputting a test signal, by capacitive coupling, to an end portion ofthe insulated wire under test among end portions of the insulated wiresexposed at one end of the multicore cable; and

measuring voltages of output signals output by capacitive couplingrespectively from end portions of the insulated wires exposed at theother end of the multicore cable, and identifying the other end portionof the insulated wire under test based on the measured voltages.

According to another embodiment of the invention, a method formanufacturing a multicore cable assembly that comprises a multicorecable comprising a single common shield covering a plurality ofinsulated wires and connectors or circuit boards provided at both endsof the multicore cable comprises:

arranging wires;

stripping the insulated wires to expose conductors at end portions; and

connecting the exposed conductors to terminals of the connectors orelectrode patterns of the circuit board,

wherein the arranging wire comprises identifying a corresponding endportion by identifying a correspondence relation between one end portionand the other end portion of the insulated wires exposed from both endsof the multicore cable and arranging end portions of the insulated wiresexposed from the both ends of the multicore cable in desired order, theidentifying a corresponding end portion comprises allowing the commonshield to have a same potential as a measurement system ground,inputting a test signal, by capacitive coupling, to an end portion ofthe insulated wire under test among end portions of the insulated wiresexposed at one end of the multicore cable, measuring voltages of outputsignals output by capacitive coupling respectively from end portions ofthe insulated wires exposed at the other end of the multicore cable, andidentifying the other end portion of the insulated wire under test basedon the measured voltages.

According to another embodiment of the invention, a multicore cable testdevice for testing a multicore cable comprising a single common shieldcovering a plurality of insulated wires to identify a correspondencerelation between one end portion and the other end portion of theinsulated wires exposed from both ends of the multicore cable comprises:

a test signal input means that inputs a test signal, by capacitivecoupling, to an end portion of the insulated wire under test among endportions of the insulated wires exposed at one end of the multicorecable in a state that the common shield is allowed to have a samepotential as a measurement system ground; and

a corresponding-end identifying unit that measures voltages of outputsignals output by capacitive coupling respectively from end portions ofthe insulated wires exposed at the other end of the multicore cable, andidentifies the other end portion of the insulated wire under test basedon the measured voltages.

Effects of the Invention

According to an embodiment of the invention, a method for testing amulticore cable can be provided that can reduce the effect of crosstalkwhen performing input of an AC test signal and output of an AC outputsignal without contact so as to accurately identify a correspondencerelation between one end portion and the other end portion of insulatedwires, as well as a method for manufacturing a multicore cable assemblyand a multicore cable test device.

BRIEF DESCRIPTION OF THE DRAWINGS

Next, the present invention will be explained in more detail inconjunction with appended drawings, wherein:

FIG. 1 is a schematic configuration diagram illustrating a multicorecable test device which is used in a method for testing a multicorecable in an embodiment of the present invention;

FIG. 2A is a schematic cross-sectional view showing a multicore cabletaken perpendicular to a longitudinal direction;

FIG. 2B is a cross sectional view showing an insulated wire takenperpendicular to the longitudinal direction;

FIGS. 3A and 3B are explanatory diagrams illustrating the insulatedwires fixed to a test bench;

FIG. 4A is a diagram illustrating an equivalent circuit when testing themulticore cable by the multicore cable test device;

FIG. 4B is an explanatory diagram illustrating the principle of themethod for testing a multicore cable;

FIG. 5 is a diagram illustrating an equivalent circuit in which a commonshield is not grounded for the purpose of comparison with the invention;

FIG. 6A is a flowchart showing a method for manufacturing a multicorecable assembly;

FIG. 6B is a flowchart showing a process of a corresponding-endidentifying step in the manufacturing method;

FIG. 7 is a flowchart showing a control flow of an arithmetic devicewhen testing a correspondence relation between one end portion and theother end portion of insulated wires; and

FIG. 8 is a graph showing a result of measuring voltage of detectionsignal obtained by the method for testing a multicore cable in theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment

An embodiment of the invention will be described below in conjunctionwith the appended drawings.

Multicore Cable Test Device

FIG. 1 is a schematic configuration diagram illustrating a multicorecable test device which is used in a method for testing a multicorecable in the present embodiment. FIG. 2A is a schematic cross-sectionalview showing a multicore cable taken perpendicular to a longitudinaldirection and FIG. 2B is a cross sectional view showing an insulatedwire taken perpendicular to the longitudinal direction.

A multicore cable test device 1 is used to identify a correspondencerelation between one end portion and the other end portion of eachinsulated wire 3 exposed at both ends of a multicore cable 2. Afteridentifying the correspondence relation between one end portion and theother end portion of the insulated wires 3 of the multicore cable 2, theinsulated wires 3 at both ends of the multicore cable 2 are respectivelyconnected to connectors or circuit boards (internal boards in sensorportions, etc.) (not shown in the drawings) according to the identifiedcorrespondence relation, and a multicore cable assembly is therebyobtained.

As shown in FIGS. 2A and 2B, the insulated wire 3 used in the multicorecable 2 is a coaxial wire 30 in which an insulation 32, an outerconductor 33 and an outer covering 34 are sequentially provided around acenter conductor 31. However, the insulated wire 3 is not limitedthereto and may not have the insulation 32 and the outer conductor 33.The outer diameter of the coaxial wire 30 is, e.g., 0.2 mm to 0.5 mm.The multicore cable 2 is formed by sequentially providing a braidedcommon shield 21 and a jacket 22 around multiple bundled coaxial wires30. The number of insulated wires 3 in the multicore cable 2 is notspecifically limited, and the invention is applicable to the multicorecable 2 having not less than three insulated wires 3. In the presentembodiment, the number of insulated wires 3 contained in one multicorecable 2 is, e.g., about ten to three hundred.

Back to FIG. 1, the multicore cable test device 1 is provided with atest signal input means 4, an output-side processing circuit 6, areference signal generating circuit 7, and an arithmetic device 8 havinga corresponding-end identifying unit 81.

The test signal input means 4 inputs an AC test signal V, by capacitivecoupling, to an end portion of the insulated wire 3 under test among endportions of the insulated wires 3 exposed at one end of the multicorecable 2. In the present embodiment, the test signal input means 4 has avoltage source 41 for generating the test signal V, a first amplifier 42for amplifying the test signal V, a first switching device 43 forswitching the insulated wire 3 to which the test signal V amplified bythe first amplifier 42 is input, and an electrode substrate 44 havingplural electrodes 442 which are respectively electrically connected tooutputs of the first switching device 43. The electrode substrate 44 isconfigured so that the test signal V is input to the insulated wire 3 bycapacitive coupling when bringing the electrode 442 into contact with anouter circumferential surface of the insulated wire 3.

In the present embodiment, since capacitive coupling is used to inputthe test signal to the insulated wires 3, an AC signal is used as thetest signal. The frequency of the test signal needs to be smaller thanthe resonant frequency of the multicore cable 2, and can beappropriately determined depending on the structure, etc., of themulticore cable 2. In more detail, the frequency of the test signal Vis, e.g., not more than 10 MHz. In the present embodiment, the testsignal V+ at 2.5 MHz is used.

As shown in FIGS. 3A and 3B, the insulated wires 3 (the coaxial wires 30in this example) exposed and aligned at one end of the multicore cable 2are fixed to a test bench 45. The test bench 45 integrally has a base451 and a pair of locking walls 452 arranged on the base 451 so as toface each other. Plural locking grooves 452 a for locking the insulatedwires 3 are formed at equal intervals on the both locking walls 452. Theinsulated wires 3 are respectively fitted and fixed to the lockinggrooves 452 a and are thereby arranged in a row on the base 451 atpredetermined intervals. However, the structure to fix the insulatedwires 3 to the test bench 45 is not limited thereto. For example, theinsulated wires 3 may be placed on an adhesive tape such as double-sidedtape stuck to the base 451 so that the insulated wires 3 are adhered andfixed to the test bench 45. In addition, although the insulated wires 3are arranged in a row at equal intervals in one direction (a directionperpendicular to a longitudinal direction of the insulated wire 3),arrangement of the insulated wires 3 may be appropriately changed.

The electrode substrate 44 has a dielectric substrate 441 and theelectrodes 442 constructed from a wiring pattern formed on thedielectric substrate 441. The same number of electrodes 442 as theinsulated wires 3 (or more than the insulated wires 3) are formed inalignment on the dielectric substrate 441 at the same intervals as theinsulated wires 3 fixed to the locking grooves 452 a. In addition, theelectrodes 442 are respectively electrically connected to the outputs ofthe first switching device 43 and the test signal V is applied to theelectrode 442 selected by the first switching device 43.

In the present embodiment, the electrode substrate 44 is pressed, with asurface having the electrodes 442 facing downward, against the insulatedwires 3 between the two locking walls 452. Thus, the electrodes 442 andthe insulated wires 3 are sandwiched between the dielectric substrate441 and the base 451. When the test signal V is applied to a givenelectrode 442 in this state, the test signal V is input to the insulatedwire 3 corresponding to the given electrode 442 by capacitive coupling.In the present embodiment in which the coaxial wire 30 is used as theinsulated wire 3, the test signal V is input to the outer conductor 33of the insulated wire 3.

A ground pattern to be a measurement system ground (signal ground) isformed on another circuit board which is electrically connected to theelectrode substrate 44 or to each electrode 442 of the electrodesubstrate 44 even though it is not shown in the drawing, and an endportion of the common shield 21 is electrically connected to the groundpattern.

Back to FIG. 1, the output-side processing circuit 6 has a test bench(not shown) having the same structure as the test bench 45 and providedat an end of the multicore cable 2, and is configured that outputsignals from the insulated wires 3 (signals transmitted through theouter conductors 33) are output by capacitive coupling by pressingelectrodes 611 of an electrode substrate 61 respectively against theinsulated wires 3. Since the test bench and the electrode substrate 61of the output-side processing circuit 6 have the same configurations asthe test bench 45 and the electrode substrate 44, the explanationthereof is omitted. A ground pattern to be a measurement system groundis formed on another circuit board which is electrically connected tothe electrode substrate 61 or to each electrode 611 of the electrodesubstrate 61 on the output-side processing circuit 6 side even though itis not shown in the drawing, and the other end portion of the commonshield 21 is electrically connected to the ground pattern. That is, thecommon shield 21 is grounded at both ends (or allowed to have the samepotential as the measurement system ground).

The output-side processing circuit 6 also has a second switching device62 electrically connected to each electrode 611 of the electrodesubstrate 61 to switch the insulated wire 3 from which an output signalis output, a second amplifier 63 for amplifying the output signal fromthe second switching device 62, a multiplier 64 which produces adetection signal by multiplying the output signal amplified in thesecond amplifier 63 by a reference signal having the same phase as thetest signal V, and a low-pass filter 65 which removes high-frequencycomponents in the detection signal sent from the multiplier 64.

When signals having the same phase and the same frequency are multipliedwith each other by the multiplier 64, a DC component and a componentwith a frequency double the original frequency are generated. Thelow-pass filter 65 removes the component with a doubled frequency andoutputs only the DC component as the detection signal to the arithmeticdevice 8.

The reference signal generating circuit 7 has a phase shifter 71 whichproduces a reference signal by adjusting the phase of the test signal Vbranched from the voltage source 41, and a third amplifier 72 whichamplifies the reference signal from the phase shifter 71 and outputs itto the multiplier 64. The phase shift amount by the phase shifter 71 isappropriately adjusted by taking into consideration capacitive couplingand phase shifting during transmission through the multicore cable 2, sothat the test signal V and the reference signal have the same phase inthe multiplier 64.

The arithmetic device 8 has the corresponding-end identifying unit 81which measures voltages of the output signals respectively output fromend portions of the insulated wires 3 exposed at the other end of themulticore cable 2 and identifies the other end portion of the insulatedwire 3 under test based on the measured voltages of the output signals.In the present embodiment, the corresponding-end identifying unit 81 isconfigured to identify the other end portion of the insulated wire 3under test based on voltage of the detection signal output from thelow-pass filter 65. The corresponding-end identifying unit 81 isrealized by appropriately combining a CPU, a memory such as RAM or ROM,a storage device such as hard disc, a software, and an interface, etc.

The corresponding-end identifying unit 81 has a switch controllingportion 811 which controls switching operations of the first and secondswitching devices 43 and 62, and a determination portion 812 whichdetermines the correspondence relation between one end portion and theother end portion of the insulated wire 3. In the present embodiment,the determination portion 812 controls the first switching device 43through the switch controlling portion 811 to input the test signal V toan end portion of the insulated wire 3 under test at one end of themulticore cable 2, and also controls the second switching device 62 andsequentially measures voltages of the detection signals from allinsulated wires 3 at the other end of the multicore cable 2.

The determination portion 812 identifies that the end portion with thedetection signal having the largest voltage, among end portions of theinsulated wires 3 exposed at the other end of the multicore cable 2, isthe other end portion of the insulated wire 3 under test, and stores thecorrespondence relation in a storage unit 82. To express thecorrespondence relation between one end portion and the other endportion of the insulated wire 3, e.g., the numbers sequentially assignedto end portions of the insulated wires 3 arranged in a row at one end ofthe multicore cable 2 are associated with the numbers sequentiallyassigned to end portions of the insulated wires 3 arranged in a row atthe other end of the multicore cable 2. The determination portion 812sequentially changes the insulated wire 3 to be tested, identifies thecorrespondence relation between one end portion and the other endportion of all insulated wires 3, and stores the identified relation inthe storage unit 82.

Reason why the Effect of Crosstalk is Reduced

Now, the reason why the effect of crosstalk is reduced in the presentembodiment is described. FIG. 4A is a diagram illustrating an equivalentcircuit when testing the multicore cable 2 by the multicore cable testdevice 1. Only one of the insulated wires 3 not receiving input of thetest signal V is shown as a representative example. In this description,the insulated wire 3 to which the test signal V is input is referred toas “first insulated wire 3 a”, and the insulated wire 3 to which thetest signal V is not input is referred to as “second insulated wire 3b”.

In addition, Cc is coupling capacitance at a capacitive coupling portionof an end portion of each insulated wire 3, Cα is coupling capacitancebetween the first and second insulated wires 3 a and 3 b, Cβ is couplingcapacitance between the insulated wires 3 a, 3 b and the common shield21, and vs and vn are voltages of output signals of the insulated wires3 a and 3 b. The coupling capacitance Cα between the first and secondinsulated wires 3 a, 3 b and the coupling capacitance Cβ between theinsulated wires 3 a, 3 b and the common shield 21 are of the same orderof magnitude (one is less than 10 times as large as the other).

When impedances due to the coupling capacitances Cc, Cα and Cβ are Zc,Zα and Zβ and impedances due to resistances r and R are Zr and ZR, theequivalent circuit of FIG. 4A can be expressed as shown in FIG. 4B. Asshown in FIG. 4B, output voltage vn of the second insulated wire 3 b isobtained after being divided into Zα and Zβ and is smaller than outputvoltage vs of the first insulated wire 3 a which is not divided. Thus, asignal-to-noise ratio (|vs/vn|) is greater than 1 and it is possible toidentify an end portion of the insulated wire 3 to which the test signalV is input.

In more detail, a signal-to-noise ratio (SNR) in the present embodimentis expressed by the following formula (1) when Cα>>Cc, Cβ>>Cc, andr+R<<(1/ωCc).

$\begin{matrix}{{SNR} = {{{{vs}/{vn}}} \approx {R \cdot \omega \cdot {Cc}}}} & (1)\end{matrix}$

Based on the formula (1), the SNR>1 and it is thus possible to identifyan end portion of the insulated wire 3 to which the test signal V isinput.

Meanwhile, in the case that the common shield 21 is not grounded (doesnot have the same potential as the measurement system ground), thecommon shield 21 can be ignored as shown in FIG. 5, and the SNR isexpressed by the following formula (2) when Cγ>>Cc and r+R<<(1/ωCc).

$\begin{matrix}{{SNR} = {{{v\; {1/v}\; 3}} \approx {1 + {\left( {1/2} \right) \cdot \left( {{{Cc}/C}\; \gamma} \right)}}}} & (2)\end{matrix}$

Based on the formula (2), the SNR is substantially 1 since Cγ>>Cc, andit is difficult to identify an end portion of the insulated wire 3 towhich the test signal V is input.

Method for Manufacturing the Multicore Cable Assembly

FIG. 6A is a flowchart showing a method for manufacturing the multicorecable assembly. As shown in FIG. 6A, the method for manufacturing themulticore cable assembly in the present embodiment includes a wirearranging step as Step S1, a stripping step as Step S2 and a connectingstep as Step S3 which are performed sequentially.

In the wire arranging step as Step S1, a corresponding-end identifyingstep to identify a correspondence relation between one end portion andthe other end portion of the insulated wires 3 exposed from both ends ofthe multicore cable 2 is performed in Step S11 by the method for testinga multicore cable in the present embodiment, and an orderly arrangingstep to arrange the end portions of the insulated wires 3 exposed fromboth ends of the multicore cable 2 in desired order is then performed inStep S12. In the stripping step as Step S2, the exposed length of eachinsulated wire 3 is adjusted (by cutting and removing an excess length),and also the conductor (the center conductor 31 and the outer conductor33 of the coaxial wire 30 in this example) is exposed at ends of eachinsulated wire 3. In the connecting step as Step S3, the exposedconductors are connected to terminals of connectors or electrodepatterns of circuit boards (not shown), etc., by soldering, etc. Throughthese steps, a multicore cable assembly having connectors or circuitboards at both ends of the multicore cable 2 is obtained.

Method for Testing the Multicore Cable

FIG. 6B is a flowchart showing a process of the corresponding-endidentifying step as Step S11. As shown in FIG. 6B, in thecorresponding-end identifying step as Step S11, i.e., in the method fortesting a multicore cable in the present embodiment, firstly, theinsulated wires 3 are exposed at both ends of the multicore cable 2 byremoving a predetermined length of the jacket 22 and the common shield21 in Step S111. After that, in Step S112, the exposed insulated wires 3are respectively fitted to the locking grooves 452 a of the test bench45 at both ends of the multicore cable 2, and the electrode substrates44 and 61 are pressed against the insulated wires 3 which are fixed tothe test bench 45. Then, a test is conducted to identify acorrespondence relation between one end portion and the other endportion of each insulated wire 3 in Step S113.

FIG. 7 is a flowchart showing a control flow of the arithmetic device 8when conducting a test to identify the correspondence relation betweenone end portion and the other end portion of the insulated wires 3 inStep S113. In this example, the number of the insulated wires 3 is n,and the sequential order of the insulated wires 3 arranged on the testbench 45 is expressed as 1^(st), 2^(nd), . . . n^(th).

Firstly, the determination portion 812 assigns an initial value of 1 tovariables a and b in Step S51, as shown in FIG. 7. After that, in StepS52, the determination portion 812 controls the first switching device43 through the switch controlling portion 811 and applies the testsignal V to the a^(th) insulated wire 3. That is, the test signal V isinput by capacitive coupling to an end portion of the a^(th) insulatedwire 3 under test among end portions of the insulated wires 3 exposed atone end of the multicore cable 2. Other signals including the testsignal V are not input to the insulated wires 3 other than the a^(th)insulated wire 3 under test.

Then, in Step S53, the determination portion 812 controls the secondswitching device 62 through the switch controlling portion 811, measuresvoltage of an output signal (in this example, a detection signalproduced by multiplying the output signal by a reference signal) outputfrom an end portion of the b^(th) insulated wire 3 exposed at the otherend of the multicore cable 2, and stores the measurement result in thestorage unit 82 so as to be associated with the variable b (i.e., thenumber assigned to the other end portion of the insulated wire 3).

In Step S54, the determination portion 812 determines whether or not thevariable b is equal to n. When the determination is NO in Step S54, b isincremented in Step S55 and the process then returns to Step S53. Whenthe determination is YES in Step S54, i.e., when measurement on endportions of all insulated wires 3 at the other end of the multicorecable 2 is finished, the determination portion 812 identifies that thenumber (the number assigned to the other end portion of the insulatedwire 3) with a detection signal having the largest voltage is the otherend portion of the a^(th) insulated wire 3 currently being tested, andthe identified correspondence relation is stored in the storage unit 82in Step S56.

In Step S57, the determination portion 812 determines whether or not thevariable a is equal to n. When the determination is NO in Step S57, a isincremented and the variable b is reset to the initial value of 1 inStep S58, and the process returns to Step S52. When the determination isYES in Step S57, i.e., once the correspondence relation in all insulatedwires 3 is identified, the process proceeds to Step S59. In Step S59,the arithmetic device 8 outputs the correspondence relationidentification result, which is stored in the storage unit 82, to, e.g.,a monitor, etc. After that, the process is ended.

Experimental Results

FIG. 8 is a graph showing a result of measuring voltage of detectionsignal obtained by the method for testing a multicore cable in thepresent embodiment. The vertical axis in FIG. 8 is an output voltageratio normalized to the largest voltage of the obtained detectionsignal. The horizontal axis in FIG. 8 indicates the numbers assigned tothe insulated wires 3 at the other end of the multicore cable 2. Inaddition, FIG. 8 also shows the experimental result of ComparativeExample in which the common shield 21 is not grounded (does not have thesame potential as the measurement system ground). In this experiment,the outer diameter of the coaxial wire 30 (the insulated wire 3) wasabout 0.3 mm, the number of the coaxial wires 30 was one hundred andninety-two, the outer diameter of the multicore cable 2 was about 10 mm,and the entire length of the multicore cable 2 (the entire length of thecoaxial wire 30) was about 2 meters.

As shown in FIG. 8, in Example according to the invention, voltage ofthe detection signal is large at an end portion of only one insulatedwire 3, and voltages of the detection signals of the other insulatedwires 3 are smaller. In other words, in Example, the SNR is large and itis thus possible to accurately identify the correspondence relationbetween one end portion and the other end portion of the insulated wire3. On the other hand, in Comparative Example, a difference between thelargest voltage of the detection signal and voltages of the otherdetection signals is small. Therefore, in Comparative Example, the SNRis close to 1 and it is difficult to accurately identify thecorrespondence relation between one end portion and the other endportion of the insulated wire 3.

Functions and Effects of the Embodiment

As described above, in the method for testing a multicore cable in thepresent embodiment, the common shield 21 of the multicore cable 2 isallowed to have the same potential as the measurement system ground, thetest signal V is input by capacitive coupling to an end portion of theinsulated wire 3 under test among end portions of the insulated wires 3exposed at one end of the multicore cable 2, voltages of output signalsoutput by capacitive coupling respectively from end portions of theinsulated wires 3 exposed at the other end of the multicore cable 2 aremeasured, and the other end portion of the insulated wire 3 under testis identified based on the measured voltages.

Since crosstalk is divided by grounding the common shield 21 (byallowing the common shield 21 to have the same potential as themeasurement system ground), the output voltage (vn) from end portions ofthe insulated wires 3 not receiving input of the test signal V isreduced to smaller than the output voltage (vs) from an end portion ofthe insulated wire 3 to which the test signal V is input. That is, theeffect of crosstalk is reduced and it is thus possible to accuratelyidentify the correspondence relation between one end portion and theother end portion of the insulated wires 3. The invention isparticularly suitably applicable to the multicore cable 2 in whichmultiple insulated wires 3 are densely arranged and a couplingcapacitance between the insulated wires 3 is large.

To reduce crosstalk between the insulated wires 3, a couplingcapacitance Cc between the electrodes 442/611 and the insulated wires 3could be increased by increasing the length of the electrodes 442/611and providing a larger contact area between the electrodes 442/611 andthe insulated wires 3. In this case, however, the test bench 45 and theelectrode substrates 44, 61 are increased in size. In addition, aportion of the insulated wire 3 to be exposed for the test is longer,which means that the insulated wire 3 needs to have a longer extralength which is removed at the time of installation to a substrate,etc., hence, wasteful. In the present embodiment, it is possible toaccurately identify the correspondence relation between one end portionand the other end portion of the insulated wires 3 even when theelectrodes 442 and 611 are relatively short and a contact area betweenthe electrodes 442/611 and the insulated wires 3 is relatively small.

Summary of the Embodiments

Technical ideas understood from the embodiment will be described belowciting the reference numerals, etc., used for the embodiment. However,each reference numeral, etc., described below is not intended to limitthe constituent elements in the claims to the members, etc.,specifically described in the embodiment.

[1] A method for testing a multicore cable (2) comprising a singlecommon shield (21) covering plural insulated wires (3) to identify acorrespondence relation between one end portion and the other endportion of the insulated wires (3) exposed from both ends of themulticore cable (2), the testing method comprising: allowing the commonshield (21) to have a same potential as a measurement system ground;inputting a test signal, by capacitive coupling, to an end portion ofthe insulated wire (3) under test among end portions of the insulatedwires (3) exposed at one end of the multicore cable (2); and measuringvoltages of output signals output by capacitive coupling respectivelyfrom end portions of the insulated wires (3) exposed at the other end ofthe multicore cable (2), and identifying the other end portion of theinsulated wire (3) under test based on the measured voltages.

[2] The method for testing a multicore cable defined by [1], wherein theother end portion of the insulated wire (3) under test is identifiedbased on voltage of a detection signal obtained by multiplying theoutput signal output from an end portion of each insulated wire (3)exposed at the other end of the multicore cable (2) by a referencesignal having the same phase as the test signal.

[3] The method for testing a multicore cable defined by [2], whereinamong the end portions of the insulated wires (3) exposed at the otherend of the multicore cable (2), an end portion with the detection signalhaving the largest voltage is identified as the other end portion of theinsulated wire (3) under test.

[4] A method for manufacturing a multicore cable assembly that comprisesa multicore cable (2) comprising a single common shield (21) coveringplural insulated wires (3) and connectors or circuit boards provided atboth ends of the multicore cable (2), the manufacturing methodcomprising: arranging wires; stripping the insulated wires (3) to exposeconductors at end portions; and connecting the exposed conductors toterminals of the connectors or electrode patterns of the circuit board,wherein the arranging wire comprises identifying a corresponding endportion by identifying a correspondence relation between one end portionand the other end portion of the insulated wires (3) exposed from bothends of the multicore cable (2) and arranging end portions of theinsulated wires (3) exposed from the both ends of the multicore cable(2) in desired order, the identifying a corresponding end portioncomprises allowing the common shield (21) to have a same potential as ameasurement system ground, inputting a test signal, by capacitivecoupling, to an end portion of the insulated wire (3) under test amongend portions of the insulated wires (3) exposed at one end of themulticore cable (2), measuring voltages of output signals output bycapacitive coupling respectively from end portions of the insulatedwires (3) exposed at the other end of the multicore cable (2), andidentifying the other end portion of the insulated wire (3) under testbased on the measured voltages.

[5] A multicore cable test device (1) for testing a multicore cable (2)comprising a single common shield (21) covering plural insulated wires(3) to identify a correspondence relation between one end portion andthe other end portion of the insulated wires (3) exposed from both endsof the multicore cable (2), the device comprising: a test signal inputmeans (4) that inputs a test signal, by capacitive coupling, to an endportion of the insulated wire (3) under test among end portions of theinsulated wires (3) exposed at one end of the multicore cable (2) in astate that the common shield (21) is allowed to have a same potential asa measurement system ground; and a corresponding-end identifying unit(81) that measures voltages of output signals output by capacitivecoupling respectively from end portions of the insulated wires (3)exposed at the other end of the multicore cable (2), and identifies theother end portion of the insulated wire (3) under test based on themeasured voltages.

Although the embodiment of the invention has been described, theinvention according to claims is not to be limited to the embodiment.Further, please note that all combinations of the features described inthe embodiment are not necessary to solve the problem of the invention.

The invention can be appropriately modified and implemented withoutdeparting from the gist thereof. For example, although the common shield21 is grounded at both ends in the embodiment, the common shield 21 maybe grounded at only one end when, e.g., the multicore cable 2 is shortin length.

What is claimed is:
 1. A method for testing a multicore cable comprisinga single common shield covering a plurality of insulated wires toidentify a correspondence relation between one end portion and the otherend portion of the insulated wires exposed from both ends of themulticore cable, the testing method comprising: allowing the commonshield to have a same potential as a measurement system ground;inputting a test signal, by capacitive coupling, to an end portion ofthe insulated wire under test among end portions of the insulated wiresexposed at one end of the multicore cable; and measuring voltages ofoutput signals output by capacitive coupling respectively from endportions of the insulated wires exposed at the other end of themulticore cable, and identifying the other end portion of the insulatedwire under test based on the measured voltages.
 2. The method accordingto claim 1, wherein the other end portion of the insulated wire undertest is identified based on voltage of a detection signal obtained bymultiplying the output signal output from an end portion of eachinsulated wire exposed at the other end of the multicore cable by areference signal having the same phase as the test signal.
 3. The methodaccording to claim 2, wherein among the end portions of the insulatedwires exposed at the other end of the multicore cable, an end portionwith the detection signal having the largest voltage is identified asthe other end portion of the insulated wire under test.
 4. A method formanufacturing a multicore cable assembly that comprises a multicorecable comprising a single common shield covering a plurality ofinsulated wires and connectors or circuit boards provided at both endsof the multicore cable, the manufacturing method comprising: arrangingwires; stripping the insulated wires to expose conductors at endportions; and connecting the exposed conductors to terminals of theconnectors or electrode patterns of the circuit board, wherein thearranging wire comprises identifying a corresponding end portion byidentifying a correspondence relation between one end portion and theother end portion of the insulated wires exposed from both ends of themulticore cable and arranging end portions of the insulated wiresexposed from the both ends of the multicore cable in desired order, theidentifying a corresponding end portion comprises allowing the commonshield to have a same potential as a measurement system ground,inputting a test signal, by capacitive coupling, to an end portion ofthe insulated wire under test among end portions of the insulated wiresexposed at one end of the multicore cable, measuring voltages of outputsignals output by capacitive coupling respectively from end portions ofthe insulated wires exposed at the other end of the multicore cable, andidentifying the other end portion of the insulated wire under test basedon the measured voltages.
 5. A multicore cable test device for testing amulticore cable comprising a single common shield covering a pluralityof insulated wires to identify a correspondence relation between one endportion and the other end portion of the insulated wires exposed fromboth ends of the multicore cable, the device comprising: a test signalinput means that inputs a test signal, by capacitive coupling, to an endportion of the insulated wire under test among end portions of theinsulated wires exposed at one end of the multicore cable in a statethat the common shield is allowed to have a same potential as ameasurement system ground; and a corresponding-end identifying unit thatmeasures voltages of output signals output by capacitive couplingrespectively from end portions of the insulated wires exposed at theother end of the multicore cable, and identifies the other end portionof the insulated wire under test based on the measured voltages.